This invention relates to the indexing or positioning of large rotating devices or rotors, particularly rotatable members having large inertia masses, such as in rotating hammer mills or shredders.
Large hammer or crusher mills are used extensively in the reduction of friable and non-friable materials. Such mills require frequent replacement of hammer impact surfaces used in the shredding and reduction process, as is disclosed for example in U.S. Pat. No. 4,136,833 to Knight. These hammer mills, particularly those designed for reduction of non-friable materials such as scrap metal or automobiles, are quite massive, and the positioning or indexing of the mill rotors for replacement of the worn hammers is a difficult and time consuming operation.
Heretofore, methods for indexing the hammer mill rotor to position hammers for replacement has been accomplished by substantially manual methods. For example, the rotor was slowly moved into the desired position by using a long heavy crowbar, sets of "come-alongs", cranes, hoists, etc. These manual methods of indexing rotors for hammer replacement are laborious, somewhat dangerous, and they add significantly to the down time of the mill.
Consequently, there has existed a need for safely, rapidly and accurately indexing or positioning these high inertia massive rotors to facilitate hammer or other impacting surface replacement or to perform routine maintenance, while avoiding problems such as recoil, rocking, telegraphing or destructive oscillations upon stopping.
In accordance with the various aspects of the invention, a rotor indexing system is provided for indexing the massive high inertia hammer-carrying rotor of a hammer mill or the like, and wherein the rotor is mounted on a large main shaft which is rotatably driven by a main drive motor. A motively powered indexing apparatus is disposed at and in axial alignment with the rear end of the main shaft, and includes a power transmission or coupling comprising a first coupling member coaxially mounted to and for rotation with a rotatable output member (such as the main mill or main motor shaft) and fixed against longitudinal axial movement; as well as a second coupling member normally spaced from the first coupling member and mounted for longitudinal movement into and out of full coupling power-transmitting engagement with the first coupling member.
The second coupling member is mounted to a prime mover or rotor indexing drive assembly including a motive means of relatively high speed and low torque connected through a speed reducer having an extremely low speed high torque output shaft, to which the second coupling member is connected. A normally engaged brake is connected to the assembly motor shaft, and is arranged to disengage when the assembly motor is actuated.
The arrangement may be such that the entire rotor indexing drive assembly is movable and carries the second coupling member into or out of selective engagement with the first coupling member. Alternately, the drive assembly is fixed, and the second coupling member is slidable on the assembly and into or out of engagement with the first coupling member.
In one embodiment, the coupling members comprise a pair of generally co-axial coupling bodies having circumferentially spaced specially bevelled jaws and substantially parallel working surfaces which, when the jaws mate, enhance the ability to handle extremely high torque loads. Furthermore, a special clearance is provided between the jaws of the mating coupling bodies to facilitate engagement. In addition, the first coupling body is mounted to a pilot shaft secured for rotation with the aforementioned rotor shaft. The pilot shaft is adapted to extend through and form the core of the first coupling body and snug-fittingly telescope into a recess in the second jaw upon coupling engagement of the two members. The pilot shaft is provided with a tapered leading edge to correct for any axial misalignment between the members, and a slightly smaller diameter than that of the mating recess in the jaws of the second coupling body.
In another embodiment, the coupling members comprise a pair of engagable gears mounted on spaced parallel axes.